1. Field of the Invention
This invention relates to devices, systems, and methods for estimating the rate at which rock and soil erode and, more specifically, to devices that subjects a soil or rock sample to shear stresses applied by rotating fluid about the sample to simulate the effects of flowing fluids on the soil or rock sample and to systems and methods using the same.
2. Background of the Related Art
The ability of rock or soil (“media”) to support relatively large structural loads depends on many factors, which can include the type of medium, the mineralogy of the medium, the strength of the medium (e.g., shear strength and compressive strength), the bearing capacity of the medium, the extent of weathering or fracturing or the like. For example, soil medium such as a hard glacial till or a stiff over-consolidated clay can be excellent load-carrying medium; whereas, soil medium such as organic clays, expansive clays, soft, unconsolidated clays or submerged silts are totally unsuitable. Similarly, rock medium such as fresh, unweathered granite that is not highly fractured can be an excellent load-carrying medium; whereas, clayey shales, chalks, porous or karstic limestone, friable sandstones or even a heavily weathered, highly fractured granite can be totally unsuitable.
In a marine environment, especially in a marine environment having relatively fast moving water (“fluid”), the ability of the medium to support loads is further complicated by the erosion or scour caused by the moving fluid. Indeed, when a fluid flows over an erodable soil, e.g., sand, silt, clay, soft rock, highly erodable rock or the like, at sufficient velocity, the medium can be eroded completely or can be eroded sufficiently to lose some of its strength or load-carrying capability. As a result, when designing foundations for structures, e.g., piers, caissons, piles, pressure-injected piles or the like, in a marine environment, e.g., a river, stream, coastline or the like, it would benefit the engineer or architect making the design to know the long- and short-term effects of the flowing fluid on the medium at the medium-foundation interface. As an example, the penetration depth of a bridge pier foundation that is to be located in and supported by the sediment requires knowledge of how much the channel bed will be lowered during a design flow event.
This is especially true when a foundation element 10 is socketed into the medium 5 (FIG. 1) so that the medium 5 itself supports some of or a considerable portion of the total load through side friction 6. The findings of Osterberg and Gill in “Load transfer mechanism for piers socketed into hard soils and rock” from the Proceedings of the 9th Canadian Symposium on Rock Mechanics, pp. 235-262 (1973) are fully incorporated herein by reference.
Presently, there are only a few field tests available for testing in situ bond strength between a foundation element 10 and a medium 5. The preferred or most widely practiced test is the “field pull-out test”, which is a destructive, relatively expensive test. During a field pull-out test, a foundation element 10, e.g., a pile, is installed, e.g., socketed, into the medium 5 according to the design specifications. Subsequently, a tensile load 3 is applied to the free end 2 of the foundation element 10 to pull the foundation element 10 from its socket 8. Alternatively, a hydraulic jack is placed beneath the foundation element and jacked upwards, creating shear stresses along the perimeter of the foundation element 10. Field instruments, e.g., stress-strain gauges or the like, typically, are placed at discrete locations along the length of the end portion 4 of the foundation element 10 that will be buried in the socket 8. As a pull-out or jacking load 3 is applied to the free or embedded end 2 of the foundation element 10, stress and strain measurements can be recorded from which engineers can estimate an in situ shear strength of the medium 5. Engineers can then use the results of the test to refine their design assumptions and re-design as necessary.
Others have developed empirical relationships for estimating field strength based on results of laboratory testing. For example, the shear strength (τ) of a medium socket can be estimated based on an unconfined compression test (q, test) using the following formula and a suitable factor of safety:τ=qu/20
There are no known direct measurement tests, however, that simulate the 5 impact of the environment, i.e., the erosive effects of the flowing fluid, and time on the medium and, hence, the foundation.
Accordingly, it would be desirable to provide devices, systems, and laboratory testing methods for estimating the rate of medium erosion. Moreover, it would be desirable to provide devices, systems, and laboratory testing methods for measuring the rate of medium erosion by rotating an outer cylinder portion about a fixed, non-rotating sample of the medium, wherein the rotation of the outer cylinder portion causes a fluid to replicate fluid flow over the surface of the medium sample.